1. Field of the Invention
The invention pertains to a vibration damper with stroke-dependent damping force of the type including a piston separating two working spaces, a pair of through channels covered by disks which open to connect the working spaces when acted on by pressure, and a bypass arrangement which connects the working spaces as a function of the stroke of the piston, i.e. when the piston is in a limited range of positions.
2. Description of the Related Art
A piston-cylinder assembly with distance-dependent performance characteristics is known from U.S. Pat. No. 5,971,117. The piston rod of the piston-cylinder assembly carries two pistons a certain distance apart, each of which can produce a damping force in both directions of piston rod movement. At least one bypass groove, which is longer in the axial direction than the distance between the piston rings of the two pistons, is formed in the cylinder of the piston-cylinder assembly. Thus three characteristic curve regions are produced. When the two pistons are in the stroke range where the bypass groove is located, the damping force is determined by the cross section of the bypass groove. As the stroke of the piston rod increases, one of the pistons travels out of the bypass region, and an intermediate characteristic is obtained. As soon as the second piston has also left the region of the bypass groove, the stiffest damping force characteristic goes into effect. For a vibration damper of this type with variable performance, however, two pistons with at least four valve disks and possibly valve springs are required. This expense can be too great for one or another concrete application.